Compressor, seal gas delivery, and method

ABSTRACT

A seal gas delivery system for an end seal on a turbo machine rotor shaft includes a seal gas passageway for delivering a seal gas to the end seal and a seal gas distributor for receiving at least a portion of the seal gas from the seal gas passageway, the seal gas distributor having a plurality of holes for distributing the seal gas about the rotor shaft during turbo machine standstill; the holes are located on a cylindrical surface and are typically arranged all around said rotor shaft, preferably regularly all around said rotor shaft.

BACKGROUND

Embodiments of the subject matter disclosed herein generally relate toturbo machines, and more particularly, to the delivery of seal gas intoa compressor end seal.

A compressor is a machine which accelerates the particles of a processfluid to, ultimately, increase the pressure of the process fluid, e.g.,a gas, through the use of mechanical energy. Compressors are commonlyused in the energy industry to produce, process, re-inject and transportmany different types of gases. Among the various types of compressorsare the so-called centrifugal compressors, in which mechanical energyoperates on process fluid input to the compressor by way of centrifugalacceleration, e.g., by rotating a centrifugal impeller by which theprocess fluid is passing. More generally, centrifugal compressors can besaid to be part of a class of machinery known as “turbo machines” or“turbo rotating machines”.

Many turbo machines, and particularly, centrifugal compressorsincorporate the use of shaft end seals into which a seal gas may beinjected, for example, to improve seal performance creating a barrieragainst process gas leakage. Many compressors are now provided with oneor more dry gas seals at either or both ends of the compressor toimprove machine performance and reduce process fluid leakage. Forexample, and as shown in FIGS. 1 and 2, a compressor 10 may include arotor shaft 20 rotatably disposed relative to a stator 12. A shaft endseal in the form of a dry gas seal, indicated generally as 14 in FIG. 1may be disposed between the rotor shaft 20 and the stator 12. Dry gasseal 14 may include primary and secondary seal rotor rings 26 andprimary and secondary seal stator rings 28 each biased towards arespective one of the primary and secondary seal rotor rings 26. Duringoperation of compressor 10, grooves (not shown) in the dry gas rotorseal rings 26 and stator seal rings 28 may generate a fluid dynamicforce to create a running gap which provides a sealing function withoutcontact between the sealing rings.

A seal gas, typically, filtered process gas, may be supplied to the drygas seal to support the running gap and otherwise improve theperformance of compressor 10. As shown in FIGS. 1 and 2, the seal gasmay be delivered through an opening 30 in the stator 12.

During operation of the compressor 10, heat generated by the compressionprocess and other processes to which the process gas is subjectedoftentimes generate a significant amount of heat which may be absorbedby the seal (process) gas. Moreover, seal gas may additionally be heatedby a dedicated device, such as a heater or heat exchanger to aid in theprevention or suppression of condensation which may arise during orbefore the expansion of the seal gas within the dry gas seal. Thus, sealgas entering the dry gas seal through port 30 may have a hightemperature relative to, for example, ambient air and/or gas alreadypresent within dry gas seal 14.

During a temporary compressor shutdown, this hot seal gas may continueto be supplied to the dry gas seal. Moreover, the temperature of theseal gas may be further increased during a temporary compressor shutdowndue to the absorption of residual heat, for example, from stationarycompressor components.

Heat within the seal gas continuously supplied to the compressor duringtemporary shutdown may cause a region or regions on the shaft 20proximate to the dry gas seal 14 to become unevenly heated, i.e., one ormore regions of the rotor shaft 20 may develop a temperaturedifferential with respect to neighboring regions of the rotor shaft 20.These so-called hotspots are potentially problematic. For example, sealgas entering the dry gas seal through port 30 may impinge against a drygas seal component adjacent the compressor rotor shaft, or worse,directly against a surface of the rotor shaft itself. Depending oncertain factors, such as the rate of heat transfer through thecomponents of the dry gas seal adjacent the rotor shaft, the rate offlow of the seal gas, the temperature of the seal gas, etc., one or moresuch hotspots may cause a deformation, e.g., bending, warping, etc., inthe rotor shaft. During subsequent compressor startup, a vibration inthe rotating assembly may be induced as a consequence of thedeformation. The vibration may have a magnitude sufficient to render thecompressor vulnerable to damage, particularly when the compressorapproaches its first critical speed. Such vibration may necessitate oneor more additional temporary shutdowns and restarts to allow for theuneven heating of the rotating assembly to dissipate and for thedeformation to ameliorate. In severe cases or in the event of vibrationrelated damage to the compressor, a full shutdown may be required.

Therefore, what is needed is a compressor, and more particularly, a sealgas delivery system, which evenly distributes seal gas heat within anend seal, which allows a compressor to be more easily restarted aftertemporary shutdown, which prevents a localized impingement of hot sealgas against a rotor shaft of the compressor, which prevents thermaldeformation of the rotor shaft, which provides an easy retrofitsolution, which is low in cost, which maintains the existing, weight,configuration, and manner of operation of a compressor and dry gas sealand which provides an alternative to heat distribution effected bycompressor shaft rotation.

BRIEF SUMMARY OF THE INVENTION

According to an exemplary embodiment, a seal gas delivery system for anend seal on a turbo machine rotor shaft includes a seal gas passagewayfor delivering a seal gas to the end seal and a seal gas distributor forreceiving at least a portion of the seal gas from the seal gaspassageway, the seal gas distributor having a plurality of holes fordistributing the seal gas about the rotor shaft during turbo machinestandstill, the holes being located on a cylindrical surface; in thisway, a swirl is induced in the seal gas around the shaft by thedistributor.

The holes are, in an embodiment, arranged circularly.

The holes are, in an embodiment, arranged all around said rotor shaft,and, in an embodiment, regularly all around said rotor shaft.

According to another exemplary embodiment, a turbo machine includes astator, a rotor shaft rotatable relative to the stator, an end sealdisposed between the stator and the rotor, a seal gas passageway fordelivering a seal gas to the end seal, and a seal gas distributor forreceiving at least a portion of the seal gas from the seal gaspassageway and distributing the seal gas about the rotor shaft; the sealgas distributor has a plurality of holes and its holes are located on acylindrical surface; in this way, during turbo machine standstill toinduce a swirl in the seal gas around the shaft based on an orientationof the holes in the seal.

In an embodiment, a container is provided for containing the seal gas;container is fluidly connected to the seal gas distributor.

A method of operating a turbo machine including an end seal on a rotorshaft thereof can include the steps of delivering a seal gas to the endseal during turbo machine standstill and distributing the seal gas aboutthe rotor shaft through a plurality of holes arranged all around saidrotor shaft to prevent uneven heating of the rotor shaft.

In an embodiments, in order to induce a stronger swirl in the seal gasaround the shaft, the seal gas flow ejected from at least some,preferably all, of the holes is inclined with respect to a correspondingradial direction defined in relation to a longitudinal axis of the rotorshaft.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate one or more embodiments and,together with the description, explain these embodiments. In thedrawings:

FIG. 1 is a partial-cross sectional view of a compressor.

FIG. 2 is a partial cut away view of the compressor shown in FIG. 1.

FIG. 3 is a partial cross-sectional view of a compressor according to anexemplary embodiment.

FIG. 4 is a partial perspective view of a distributor of the compressorshown in FIG. 3.

FIG. 5 is a partial cross-sectional view of a compressor according toanother exemplary embodiment.

FIG. 6 is a partial perspective view of a distributor of the compressorshown in FIG. 5.

FIG. 7 depicts a method according to an exemplary embodiment.

DETAILED DESCRIPTION

The following description of the exemplary embodiments refers to theaccompanying drawings. The same reference numbers in different drawingsidentify the same or similar elements. The following detaileddescription does not limit the invention. Instead, the scope of theinvention is defined by the appended claims. The following embodimentsare discussed, for simplicity, with regard to the terminology andstructure of turbo machine systems. However, the embodiments to bediscussed next are not limited to these exemplary systems, but may beapplied to other systems.

Reference throughout the specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with an embodiment is included inat least one embodiment of the subject matter disclosed. Thus, theappearance of the phrases “in one embodiment” or “in an embodiment” invarious places throughout the specification is not necessarily referringto the same embodiment. Further, the particular features, structures orcharacteristics may be combined in any suitable manner in one or moreembodiments.

FIGS. 3 and 4 show an exemplary embodiment of a seal gas delivery systemaccording to the present invention. Therein, a compressor 110 includes astator 112 having a seal gas passageway 122 extending through stator 112to a dry gas seal 114. Seal gas may be delivered through a primary port154 in stator 112 to dry gas seal 114.

Compressor 110 further includes a labyrinth seal 158 adjacent dry gasseal 114. As shown in FIG. 3, labyrinth seal 158 is provided with adistributor 140 in the form of a ring portion extending from labyrinthseal 158. Distributor 140 is provided with a plurality of gas injectionholes 160; holes 160 are located on a cylindrical surface, inparticular, they are arranged circularly according to one circle.

During a temporary standstill or idling of compressor 110, seal gas maycontinue to be supplied to dry gas seal 114, as previously discussed. Atleast a portion of the seal gas may be received by distributor 140 andreleased about the circumference of rotor shaft 120 through each of theplurality of seal gas injection holes 160. This action may enhance ahomogenous distribution of seal gas around the shaft, with or withoutswirl motion, and thereby inhibit localized heating of rotor shaft 120.

Moreover, distributor 140 may also prevent seal gas exiting port 154from impinging directly against rotor shaft 120. For example, and asshown in FIG. 3, labyrinth seal 158 and dry gas seal 114 define achamber 156 in which the surface of turbo shaft 120 is exposed directlyto seal gas. Since distributor 140 is disposed between rotor shaft 120and vent 130, direct impingement of potentially hot seal gas againstthis surface is inhibited or prevented.

As may be further appreciated in FIG. 4, gas injection holes 160 mayalso be configured to provide a circumferential swirl of seal gas withinchamber 156 to further promote the circulation of gas and the uniformdistribution of heat about shaft 120. As shown in FIG. 4, each gasinjection hole 160 may define an axis 164 at an angle 168 with a radialline 166 extending from a longitudinal axis of rotor shaft 120 throughthe center of the gas injection hole 160; in other words, the seal gasflow ejected from holes 160 is inclined with respect to a correspondingradial direction defined in relation to a longitudinal axis of saidrotor shaft. Alternatively, angle 168 may vary between holes 160 ofdistributor 140 in order to, for example, induce a greater degree ofturbulence providing a uniform heating of the shaft 120 in chamber 156.

FIGS. 5 and 6 show another exemplary embodiment. Therein, a gas deliverysystem includes a seal gas passageway 222 extending through stator 212to a port 254. Seal gas exiting port 254 enters a groove 255 in thestator 212.

A distributor in the form of an arc segment or full cylinder 240 havingends 278 is disposed proximately of the vent 254 within groove 255.Distributor 240 may be fixed within groove 255 mechanically, forexample, by a friction fit or a fastener or, chemically, for example, byan adhesive or a weld. In the embodiment of FIGS. 5 and 6, a midpoint ofdistributor 240 may be positioned between vent 254 and the rotor shaftof compressor 210 to receive seal gas exiting vent 254. Seal gas exitingvent 254 may initially be deflected and thus urged along the groove 255,for example, clockwise and counterclockwise. Seal gas may also passthrough any of holes 276. In this manner, seal gas may be distributedabout the rotor shaft of compressor 210 and may thereby be prevented orinhibited from forming a localized high temperature area on or near therotor shaft during a temporary shutdown of compressor 210. Distributor240 may be provided within groove 255 as part of the manufacturingprocess of compressor 210, i.e. as original equipment, or alternatively,distributor 240 may be provided as an aftermarket product introduced togroove 255 during a retrofit.

In the embodiment shown in FIGS. 5 and 6, distributor 240 is shown as anarc segment having a plurality of holes 260; holes 260 are located on acylindrical surface, in particular, they are arranged circularlyaccording to a number (specifically five) of parallel circles; holes 260are arranged all around the rotor shaft; according to the example ofFIG. 6, they are arranged regularly all around the rotor shaft. However,distributor 240 may be provided in other configurations as well. Forexample, distributor 240 may be provided without holes 276 such that theentirety of seal gas received by the distributor 240 is deflected alonggroove 255. As another example, distributor 240 may be provided in afull ring configuration or a series of ring segments. The size andconfiguration of the holes 260 in distributor 240 may also vary. Forexample, if distributor 240 is provided as a series of ring segments,the space between each segment may define a plurality of holes throughwhich the flow of seal gas may be controlled.

Thus, according to an exemplary embodiment as shown in the flowchart ofFIG. 7, a method (1000) of operating a turbo machine including an endseal on a rotor shaft thereof can include steps of delivering (1002) aseal gas to the end seal during turbo machine standstill anddistributing (1004) the seal gas about the rotor shaft through aplurality of holes arranged all around said rotor shaft to preventuneven heating of the rotor shaft.

Although the seal gas distributor has been described as component of thecompressor, a seal gas distributor according to the present inventionmay be provided as a component of the end seal itself. For example, oneof ordinary skill in the art will appreciate that a seal gas deliverysystem may be configured such that the distributor may be incorporatedinto a dry gas seal cartridge.

In an embodiment, the seal gas comes fluidly to the seal gas distributorfrom a container which is part of a turbo machine; such container may besmall or big, and not necessarily dedicated only to the function ofcontaining the seal gas.

The above-described embodiments are intended to be illustrative in allrespects, rather than restrictive, of the present invention. All suchvariations and modifications are considered to be within the scope ofthe present invention as defined by the following claims. No element,act, or instruction used in the description of the present applicationshould be construed as critical or essential to the invention unlessexplicitly described as such. Also, as used herein, the article “a” isintended to include one or more items.

What is claimed is:
 1. A seal gas delivery system for an end seal on aturbo machine rotor shaft, the seal gas delivery system comprising: aseal gas passageway for delivering a seal gas to the end seal; a sealgas distributor for receiving at least a portion of the seal gas fromthe seal gas passageway, the seal gas distributor comprising a pluralityof holes for distributing the seal gas about the rotor shaft duringturbo machine standstill, wherein the holes are located on a cylindricalsurface.
 2. The seal gas delivery system of claim 1, wherein the holesare arranged circularly.
 3. The seal gas delivery system of claim 1,wherein the holes are arranged around the rotor shaft.
 4. The seal gasdelivery system of claim 1, wherein the holes are spaced apart relativeto a circumferential surface of the rotor shaft.
 5. The seal gasdelivery system of claim 1, wherein the holes are spaced apart relativeto a longitudinal surface of the rotor shaft.
 6. The seal gas deliverysystem of claim 1, wherein each of the holes defines an axis and theaxis is at a non-zero angle relative to a radial line extending from alongitudinal axis of the rotor shaft through a center of the each of theholes.
 7. The seal gas delivery system of claim 6, wherein a labyrinthseal is disposed proximately of the end seal, and the seal gasdistributor further comprises a ring portion extending from thelabyrinth seal.
 8. The seal gas delivery system of claim 5, wherein theseal gas distributor further comprises an arc segment or full cylinder.9. The seal gas delivery system of claim 5, wherein seal gas distributorfurther comprises a ring.
 10. The seal gas delivery system of claim 1,wherein the end seal is a dry gas seal.
 11. A turbo machine, comprising:a stator; a rotor shaft rotatable relative to the stator; an end sealdisposed between the stator and the rotor shaft; a seal gas passagewayfor delivering a seal gas to the end seal; and a seal gas distributorfor receiving at least a portion of the seal gas from the seal gaspassageway, and distributing the seal gas about the rotor shaft duringturbo machine standstill, wherein the seal gas distributor comprises aplurality of holes, and wherein the holes are located on a cylindricalsurface.
 12. The turbo machine of claim 11, wherein the holes arearranged circularly.
 13. The turbo machine of claim 11, furthercomprising a container containing the seal gas, wherein the container isfluidly connected to the seal gas distributor.
 14. A method of operatinga turbo machine including an end seal on a rotor shaft thereof, themethod comprising: delivering a seal gas to the end seal during turbomachine standstill; and distributing the seal gas about the rotor shaftthrough a plurality of holes arranged around the rotor shaft to preventuneven heating of the rotor shaft.
 15. The method of operating a turbomachine of claim 14, wherein the seal gas flow ejected from at leastsome of the holes is inclined with respect to a corresponding radialdirection defined in relation to a longitudinal axis of the rotor shaft.16. The method of operating a turbo machine of claim 14, wherein theseal gas flow ejected from all of the holes is inclined with respect toa corresponding radial direction defined in relation to a longitudinalaxis of the rotor shaft.
 17. The seal gas delivery system of claim 1,wherein the holes are arranged regularly around the rotor shaft.
 18. Theseal gas delivery system of claim 2, wherein the holes are arrangedaround the rotor shaft.
 19. The seal gas delivery system of claim 2,wherein the holes are spaced apart relative to a circumferential surfaceof the rotor shaft.
 20. The seal gas delivery system of claim 2, whereineach of the holes defines an axis and the axis is at a non-zero anglerelative to a radial line extending from a longitudinal axis of therotor shaft through a center of the each of the holes.